1. Field of the Invention
This invention arises in the field of electrophoresis apparatus, and relates in particular to cell designs for electrophoresis in slab gels.
2. Description of the Prior Art
Electrophoresis in slab gels offers versatility and speed to the laboratory technician performing analyses of biological samples. A single slab gel can serve as the separation medium in which a large number of individual samples can be analyzed simultaneously by dividing the slab into parallel lanes and using one lane for each sample. This affords not only speed and an efficient use of labor, energy, materials, equipment, and time, but also eliminates many of the problems that commonly arise when separate procedures are performed on each of a series of samples, the problems including for example nonuniformity that arises from variations in gel quality and operating conditions and the risk of operator error. One of the most important uses of slab gels however is in the performance of two-dimensional electrophoresis, in which a first dimension separation is performed in a linear medium such as a gel tube or strip, which is then placed along one edge of the slab for a second dimension separation in a direction transverse to the axis of the linear medium. In two-dimensional electrophoresis, one of the most common separation techniques for the first dimension separation is isoelectric focusing. The second dimension separation is then performed by any of the various forms of traditional electrophoresis, with the result that each of the zones formed in the first dimension is separated into its components. Thus, in addition to the efficiency that slab gels provide in the performance of multiple separations, slab gels permit the separation of highly complex protein mixtures that could not be separated in a single dimension separation.
Efficiency and uniformity in slab gel electrophoresis are improved even more when a series of slab gels are run simultaneously in a common electrophoresis cell with a common buffer solution and a common temperature and electrical potential. Various cell designs have been proposed, and a representative example is that disclosed in U.S. Pat. No. 4,088,561, to Norman L. Anderson, issued May 9, 1978. The Anderson patent shows a cell that accommodates ten slab gels in an elongated rectangular chamber with wire grids on each side of the gel slab array to serve as electrodes. Typical problems encountered in the use of these cells include the difficulty of achieving a uniform electrical field extending over all of the gels, and the difficulty of controlling the temperature of the gels since the heat generated by current running through each gel is compounded when a multitude of gels is present.
The difficulties enumerated above and others associated with electrophoresis cells designed to accommodate several slab gels are addressed by the present invention, which resides in a multi-slab gel electrophoresis cell in which plate electrodes are used to establish the electric potential, and in which buffer solution is circulated through the cell interior in a circulation path that causes buffer to flow continuously through the cell in an upward direction while contacting each gel slab cassette in the cell. In preferred embodiments of the invention, internal cooling of the cell is also provided, most preferably by a loop of circulating coolant positioned near the floor of the cell so that the circulating buffer solution is cooled near the bottom of the cell before flowing upward past the slab gels. In still further preferred embodiments of the invention, specially designed retaining members are included in the cell design both to hold the gel cassettes in place and to minimize or prevent the bypass of current flow around the gels and between the different compartments of the cell that serve as the anode compartment and the cathode compartment. The retaining members are also designed to minimize or prevent fluid and current leakage when the number of gel cassettes installed in the cell is less than the maximum number that the cell accommodates.
These and other objects, advantages, features and embodiments of the invention will be apparent from the description that follows.